ASTM D5012-01(2008)
(Guide)Standard Guide for Preparation of Materials Used for the Collection and Preservation of Atmospheric Wet Deposition
Standard Guide for Preparation of Materials Used for the Collection and Preservation of Atmospheric Wet Deposition
SIGNIFICANCE AND USE
Some chemical constituents of AWD are not stable and must be preserved before chemical analysis. Without sample preservation, it is possible that analytes can be lost through decomposition or sorption to the storage bottles.
Contamination of AWD samples can occur during both sample preservation and sample storage. Proper selection and cleaning of sampling containers are required to reduce the possibility of contamination of AWD samples.
The natural sponge and talc-free plastic gloves used in the following procedures should be recognized as potential sources of contamination. Individual experience should be used to select products that minimize contamination.
SCOPE
1.1 This guide presents recommendations for the cleaning of plastic or glass materials used for collection of atmospheric wet deposition (AWD). This guide also presents recommendations for the preservation of samples collected for chemical analysis.
1.2 The materials used to collect AWD for the analysis of its inorganic constituents and trace elements should be plastic. High density polyethylene (HDPE) is most widely used and is acceptable for most samples including samples for the determination of the anions of acetic, citric, and formic acids. Borosilicate glass is a collection alternative for the determination of the anions from acetic, citric, and formic acid; it is recommended for samples for the determination of other organic compounds.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: D5012 − 01(Reapproved 2008)
Standard Guide for
Preparation of Materials Used for the Collection and
Preservation of Atmospheric Wet Deposition
This standard is issued under the fixed designation D5012; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope D1695 Terminology of Cellulose and Cellulose Derivatives
D2914 Test Methods for Sulfur Dioxide Content of the
1.1 This guide presents recommendations for the cleaning
Atmosphere (West-Gaeke Method)
of plastic or glass materials used for collection of atmospheric
D4453 Practice for Handling of High Purity Water Samples
wet deposition (AWD). This guide also presents recommenda-
tions for the preservation of samples collected for chemical
3. Terminology
analysis.
3.1 Definitions:
1.2 ThematerialsusedtocollectAWDfortheanalysisofits
3.1.1 For definitions of terms used in this guide, refer to
inorganic constituents and trace elements should be plastic.
Terminology D1129.
High density polyethylene (HDPE) is most widely used and is
3.1.2 For definition of plastic refer to Terminology D1695
acceptable for most samples including samples for the deter-
and Terminology D883.
mination of the anions of acetic, citric, and formic acids.
3.1.3 For definition of AWD (precipitation, meteorologi-
Borosilicate glass is a collection alternative for the determina-
cal) refer to Terminology D1356.
tion of the anions from acetic, citric, and formic acid; it is
recommended for samples for the determination of other
4. Significance and Use
organic compounds.
4.1 Some chemical constituents of AWD are not stable and
1.3 This standard does not purport to address all of the
must be preserved before chemical analysis. Without sample
safety concerns, if any, associated with its use. It is the
preservation, it is possible that analytes can be lost through
responsibility of the user of this standard to establish appro-
decomposition or sorption to the storage bottles.
priate safety and health practices and determine the applica-
4.2 Contamination of AWD samples can occur during both
bility of regulatory limitations prior to use.
sample preservation and sample storage. Proper selection and
cleaning of sampling containers are required to reduce the
2. Referenced Documents
possibility of contamination of AWD samples.
2.1 ASTM Standards:
4.3 The natural sponge and talc-free plastic gloves used in
D883 Terminology Relating to Plastics
the following procedures should be recognized as potential
D1125 Test Methods for Electrical Conductivity and Resis-
sources of contamination. Individual experience should be
tivity of Water
used to select products that minimize contamination.
D1129 Terminology Relating to Water
D1193 Specification for Reagent Water
5. Apparatus
D1356 Terminology Relating to Sampling and Analysis of
5.1 Instruments shall be selected in accordance with an
Atmospheres
applicable test method given in Test Methods D1125.
This guide is under the jurisdiction of ASTM Committee D22 on Air Quality 5.2 The conductivity cell shall be pipet or dip type with a
and is the direct responsibility of Subcommittee D22.03 on Ambient Atmospheres
cell constant (K) of 0.1.
and Source Emissions.
Current edition approved April 1, 2008. Published July 2008. Originally
6. Reagents and Materials
approved in 1989. Last previous edition approved in 2001 as D5012 - 01. DOI:
10.1520/D5012-01R08.
6.1 Purity of Reagents—Reagent grade acids and other
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
chemicals shall be used to reduce the risk of contaminating the
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
AWD samples. Unless otherwise indicated, it is intended that
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. all reagents conform to the specifications of the Committee on
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D5012 − 01 (2008)
TABLE 1 Preservation of AWD Samples Collected for Inorganic Cation and Anion Determinations
Preservation Technique Species Determined Remarks Reference
No preservation All inorganic cations and anions Rapid analysis is required after collection because ion concentrations may (10-14)
change in samples. Ammonium, nitrate, and ortho-phosphate concentrations
may be reduced in samples that are biologically active. Cation and trace metal
concentrations may be reduced by sorption onto container surfaces.
Refrigerate 4°C All inorganic cations and anions Chilling may reduce the loss of ammonium, nitrate, and ortho-phosphate in (15-17)
samples that are biologically active. Samples must be allowed to come to am-
bient temperature (23–27°C) before performing pH and specific conductance
determinations. Specific conductance and pH determinations should be per-
formed on-site as soon as possible after sample collection.
2+ 2+ + +
HNO pH#2Ca ,Mg ,Na ,K Samples must first be filtered, or acid addition may dissolve particles in the AWD (11,12)
samples (see 7.4.1). Acid addition will interfere with anion determination, so a
separate aliquot will be needed for other ion determinations.
HCl, 5 mL/L All dissolved Hg and total Hg Samples for dissolved Hg are filtered through 0.45 µm capsule filter. Samples (19,20)
collected directly into specially cleaned, pretested, fluoropolymer bottle.
Filtration All inorganic cations and anions pH and specific conductance determinations may be affected by filtration. Care (18)
must be taken to minimize the possibility of sample contamination during filtra-
tion.
Analytical Reagents of the American Chemical Society where 7.2.1 Samples collected for pH, specific conductance,
such specifications are available. calcium, magnesium, potassium, sodium, chloride, fluoride,
andsulfateanalysisareoftenonlyplacedinpre-cleanedplastic
6.2 Nitric acid, ultra pure.
containers (see Section 8) before analysis. If there is a delay
6.3 Nitric acid (1+9)—Dilute 1 volume concentrated nitric
between time of collection and time of analysis, a preservation
acid with 9 volumes of water.
technique may eliminate or moderate chemical and biological
changes in the AWD samples. Table 1 summarizes the recom-
6.4 Chloroform, high performance liquid chromatography
reagent. mended sample preservation techniques for AWD samples.
6.5 Hydrochloric acid, pretested for total and methyl mer- 7.3 Samples Collected for Organic Acids:
cury.
7.3.1 Samples collected for the analysis of acetate, citrate,
formate and other low molecular weight organic acid anions
6.6 Purity of Water—Unless otherwise indicated, references
(C -C ) should be preserved within minutes after collection.
1 12
to water shall be understood to mean reagent water as defined
OrganicacidshavebeendeterminedinAWDsamplescollected
by Type I of Specification D1193.AWD samples collected for
from locations around the world (1-7). These compounds (in
organic analysis may require Type II (distilled) reagent water.
particular formic and acetic acids) can constitute from a small
7. Sample Preservation fraction to mostly all of the free acidity in AWD samples.
Because these acids are unstable in AWD samples, samples
7.1 Interactionbetweenthesampleandtheatmospheremust
must be analyzed within hours after collection or else a
be minimized. The sample container should be sealed as soon
preservation technique is required. Table 2 summarizes the
as possible after collection or sub-sampling.AWD samples can
recommended sample preservation techniques for AWD
be easily contaminated because of the low concentration levels
samples.
oftheiranalytes.Tracemetals,andpossiblyotherionsinAWD
samples, can be lost through sorption with the bottle or
7.4 Samples Collected for Trace Dissolved Metals:
container in which they are stored.AWD samples may contain
7.4.1 Samplescollectedfortracemetalsshouldbefilteredto
biologically active microorganisms which could affect the
remove insoluble particulate matter often found in AWD
concentration of many analytes. Immediate analysis of AWD
samples unless an AWD particulate trace element analysis is
samples is best and chemical preservation should be used only
desired. Filter pore size should be ≤0.45 µm. Filter materials
when the preservation is shown not to interfere with the
may contain trace elements, and the filters should be precon-
analysis being performed. Samples collected for total and
ditioned before use by filtering 300 mL of water in order to
methyl mercury determinations are to be collected directly into
leach soluble impurities on the filter and from the filtration
specially cleaned, pretested, fluoropolymer bottle(s) (19 and
apparatus itself (8). Any filters used for AWD samples should
20).
betestedtodetermineifthefiltercauseslossesorgainsoftrace
elements to theAWD sample.Test the preconditioned filters by
7.2 Samples Collected for Inorganic Cation and Anion
filtering 50 mL of water and determine the analyte concentra-
Determinations:
tions of interest in the filtrate.
7.4.2 Acidify theAWD sample with nitric acid to pH≤2to
Reagent Chemicals, American Chemical Society Specifications , American
minimize container adsorption of trace metals. The highest
Chemical Society, Washington, DC. For suggestions on the testing of reagents not
purity acid available should be used. Most AWD samples are
listed by the American Chemical Society, see Analar Standards for Laboratory
Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
poorly buffered and only small quantities of acid (about 1
and National Formulary, U.S. Pharmaceutical Convention, Inc. (USPC), Rockville,
mL/L) are required to reduce the AWD sample to a pH ≤2.
MD.
Samples acidified with an acid may not be used for the
The boldface numbers in parentheses refer to the list of references at the end of
this standard. determination of pH and certain other analytes.
D5012 − 01 (2008)
TABLE 2 Preservation of AWD Samples Collected for Organic Acid Determinations
Preservation Technique Species Determined Remarks Reference
Chloroform Acetate, citrate, formate, C –C Analysis is usually by ion-exclusion chromatography because chloroform may (3,4)
1 5
interfere with capillary GC-MS analysis. This preservative is often coupled with
sample storage at 4°C. When chloroform treatment is combined with storage in
the dark at 4°C, samples are reportedly stable for 60 days. Final chloroform
concentration in the AWD sample must be 0.2 % by weight.
Freeze at − 20°C Short-chain dicarboxylic acids Analysis is by capillary gas chromatography or GC-MS. Sample must be (6)
C –C completely in the liquid state before sample is prepared for analysis. Maximum
2 12
storage time has not been reported.
Chill at 4°C Low molecular weight acids This is a minimum procedure for organic acid preservation. This preservation (7)
technique will not preserve acetate and formate longer than 3 days.
Degradation may occur in less than 3 days.
7.4.3 Acidify the AWD sample with 5 mL/L of pretested 8.2.9 Measure the specific conductance of the water in the
HCl for dissolved mercury and total mercury. bucket. Transfer a portion of the rinse water to a clean
measuring vessel and determine the specific conductance. If
8. Sample Containers
the specific conductance is greater than 2 µS/cm (Test Method
D1125), repeat 8.2.4-8.2.8.
8.1 ManyAWD sampling networks use samplers that utilize
8.2.10 Shake the inverted bucket to remove any excess
either a bucket or bottle that is an integral component of the
water and place the bucket in a clean plastic bag, making sure
AWD samplers. These collection techniques allow “wet-only”
that only the interior of the bag contacts the interior of the
samples to be obtained, meaning the bucket or bottle is only
bucket. Seal the bag with rubber bands or twist ties.
exposed to the atmosphere during the precipitation event. The
8.2.11 Scrub the inner surface of the lid with the sponge.
preparation or cleaning procedures described in Section 8
Rinse the lid with water.
applytotheautomatedAWDsamplersthatusebuckets,andthe
sample storage bottles to which theAWD sample is transferred 8.2.12 Soak the lids for at least 24 h in water.
from the collection bucket. The procedure described in 8.3
8.2.13 Rinse lids with water, shake free the excess water,
could also be used as a cleaning procedure forAWD sampling
and place lid in a plastic bag. Seal the bag with a rubber band
that uses a bottle as the principal collection container.
or twist tie.
NOTE 1—Any materials used for the collection and preservation of
NOTE 3—All cleaning and packaging steps should be performed while
AWD should be dedicated to the use intended.
wearing talc-free plastic gloves. Both hands should be gloved. Gloves
shouldbewornforallproceduresthatareusedtopreparematerialsforthe
8.2 Inorganic Ions—Buckets and Lids:
collection and preservation of AWD.
8.2.1 Sample containers shall be made of materials that will
8.3 Inorganic Ions—Plastic Bottles:
not contaminate the sample and shall be cleaned thoroughly
before use. Plastic containers of polyethylene and polypropyl-
8.3.1 Sample containers shall be made of materials that will
ene are recommended for AWD samples collected for inor-
not contaminate the sample and shall be cleaned thoroughly
ganic ions. HDPE is most commonly used.
before use. HDPE is most commonly used.
8.2.2 Wipe the exterior of the bucket with damp cloth or
8.3.2 Soak the bottle closures (caps) in water while the
brush.
bottles are being prepared.
8.2.3 Clean collector buckets and lids only with water. The
8.3.3 Rinse each bottle a minimum of three times with
inside of the bucket and inner side of the lid should not come
water.Theamountofwaterusedforeachrinseisdependenton
intocontactwithanyobjectotherthananaturalspongethathas
the bottle volume. For 250-mL or smaller bottles, use about
been preconditioned with water by soaking the sponge for at
one-half the bottle volume. For bottles larger than 250 mL, use
least 24 h.
at least 200 mL of water.
8.3.4 Fill each bottle as full as possible with water and seal
NOTE 2—The initial preparation procedure for newly obtained natural
spongesrequiresthatthespongeiswashedwithcopiousamountsofwater
with the cap. Store the full bottles at least overnight (see Note
at least four times. Soaking a new natural sponge in 4 L of water for two
3).
or three days, after washing, is suggested.
8.3.5 Randomly select bottles and determine the conductiv-
8.2.4 Rinsetheinteriorofthebuckettwoormoretimeswi
...
This document is not anASTM standard and is intended only to provide the user of anASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
An American National Standard Designation: D 5012 – 01 (Reapproved 2008)
e1
Designation:D5012–89(Reapproved 1994)
Standard Guide for
Preparation of Materials Used for the Collection and
Preservation of Atmospheric Wet Deposition
This standard is issued under the fixed designation D 5012; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
e NOTE—Section 9 was editorially added in April 1994.
1. Scope
1.1 This guide presents recommendations for the cleaning of plastic or glass materials used for collection of atmospheric wet
deposition (AWD). This guide also presents recommendations for the preservation of samples collected for chemical analysis.
1.2 The materials used to collectAWD for the analysis of its inorganic constituents and trace elements should be plastic. High
density polyethylene (HDPE) is most widely used and is acceptable for allmost samples including samples for the determination
oftheanionsofacetic,citric,andformicacids.Borosilicateglassisacollectionalternativeforthedeterminationoftheanionsfrom
acetic, citric, and formic acid; it is recommended for samples for the determination of other organic compounds.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory
limitations prior to use.
2. Referenced Documents
2.1 ASTM Standards:
D 883 Terminology Relating to Plastics
D 1125 Test Methods for Electrical Conductivity and Resistivity of Water
D 1129 Terminology Relating to Water
D 1193 Specification for Reagent Water
D 1356 Terminology Relating to Sampling and Analysis of Atmospheres
D 1695 TerminologyofCelluloseandCelluloseDerivativesD2914TestMethodsforSulfurDioxideContentoftheAtmosphere
(West-Gaeke Method)
D4453Practice for Handling of Ultra-Pure Water Samples 2914 Test Methods for Sulfur Dioxide Content of theAtmosphere
(West-Gaeke Method)
D 4453 Practice for Handling of Ultra-Pure Water Samples
3. Terminology
3.1 Definitions:
3.1.1 For definitions of terms used in this guide, refer to Terminology D 1129.
3.1.2 For definition of plastic refer to Terminology D 1695 and Terminology D 883.
3.1.3 For definition of AWD (precipitation, meteorological) refer to Terminology D 1356.
4. Significance and Use
4.1 Some chemical constituents of AWD are not stable and must be preserved before chemical analysis. Without sample
preservation, it is possible that analytes can be lost through decomposition or sorption to the storage bottles.
4.2 Contamination of AWD samples can occur during both sample preservation and sample storage. Proper selection and
cleaning of sampling containers are required to reduce the possibility of contamination of AWD samples.
This guide is under the jurisdiction of ASTM Committee D-22 on Sampling and Analysis of Atmospheres and is the direct responsibility of Subcommittee D22.06 on
Atmospheric Deposition.
Current edition approved Nov. 24, 1989. Published March 1990.
This guide is under the jurisdiction of ASTM Committee D22 on Air Quality and is the direct responsibility of Subcommittee D22.03 on Ambient Atmospheres and
Source Emissions.
Current edition approved April 1, 2008. Published July 2008. Originally approved in 1989. Last previous edition approved in 2001 as D 5012 - 01.
For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at service@astm.org. For Annual Book ofASTM Standards
, Vol 08.01.volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D5012–01 (2008)
4.3 The natural sponge and talc-free plastic gloves used in the following procedures should be recognized as potential sources
of contamination. Individual experience should be used to select products that minimize contamination.
5. Apparatus
5.1 Instruments shall be selected in accordance with an applicable test method given in Test Methods D 1125.
5.2 The conductivity cell shall be pipet or dip type with a cell constant (K) of 0.1 .
TABLE 1 Preservation of AWD Samples Collected for Inorganic Cation and Anion Determinations
Preservation Technique Species Determined Remarks Reference
No preservation All inorganic cations and Rapid analysis is required after collection because ion concentrations may (10-14)
anions change in samples. Ammonium, nitrate, and ortho-phosphate concentrations
may be reduced in samples that are biologically active. Cation and trace metal
concentrations may be reduced by sorption onto container surfaces.
Refrigerate 4°C All inorganic cations and Chilling may reduce the loss of ammonium, nitrate, and ortho-phosphate in (15-17)
anions samples that are biologically active. Samples must be allowed to come to
ambient temperature (23–27°C) before performing pH and specific
conductance determinations. Specific conductance and pH determinations
should be performed on-site as soon as possible after sample collection.
2+ 2+ + +
HNO pH#2Ca ,Mg ,Na ,K Samples must first be filtered, or acid addition may dissolve particles in the (11,12)
AWD samples (see 7.4.1). Acid addition will interfere with anion determination,
so a separate aliquot will be needed for other ion determinations.
HgCl2 or tetrachloro Ammonium, nitrate,ni trite, Mercury (II) isa known biocide and will preserve samples for 9 to 16 days and (1,17)
mercu- phosphate possibly longer periods of time. Dissolved mercury m ayinterfere wi thotherion
A
rate (Na HgCl ) determinations, and this will require an ad ditional al iquot. Final dissolved
2 4
mercury (II) concentration in the AWDsamplemust be atleast 30 mg/L.
HCl, 5 mL/L All dissolved Hg and total Hg Samples for dissolved Hg are filtered through 0.45 µm capsule filter. Samples (19,20)
collected directly into specially cleaned, pretested, fluoropolymer bottle.
Filtration All inorganic cations and pH and specific conductance determinations may be affected by filtration. Care (18)
anions must be taken to minimize the possibility of sample contamination during
filtration.
A
Several of the suggested preservatives, such as tetrachloromercurate and mercuric chloride, are environmental and human health hazards and the use and disposal
of these preservatives should be carefully controlled (Test Method D2914, Section A4).
6. Reagents and Materials
6.1 Purity of Reagents—Reagent grade acids and other chemicals shall be used to reduce the risk of contaminating the AWD
samples. Unless otherwise indicated, it is intended that all reagents conform to the specifications of the Committee onAnalytical
Reagents of the American Chemical Society where such specifications are available.
6.2 Nitric acid, ultra pure.
6.3 Nitric acid (1+9)—Dilute 1 volume concentrated nitric acid with 9 volumes of water.
6.4 Chloroform, high performance liquid chromatography reagent.
6.5Sodium tetrachloromercurate (II), 40 g/L Hg—Dissolve 54.4 g of mercuric chloride (HgCl ) and 23.4 g sodium chloride
(NaCl) in distilled water and adjust volume to 1000 mL.
6.6Mercuric chloride.
6.7Sodium chloride.
6.8
6.5 Hydrochloric acid, pretested for total and methyl mercury.
6.6 Purity of Water—Unless otherwise indicated, references to water shall be understood to mean reagent water as defined by
Type I of Specification D 1193. AWD samples collected for organic analysis may require Type II (distilled) reagent water.
7. Sample Preservation
7.1 Interaction between the sample and the atmosphere must be minimized. The sample container should be sealed as soon as
possibleaftercollectionorsub-sampling.AWDsamplescanbeeasilycontaminatedbecauseofthelowconcentrationlevelsoftheir
analytes.Trace metals, and possibly other ions inAWD samples, can be lost through sorption with the bottle or container in which
they are stored. AWD samples may contain biologically active microorganisms which could affect the concentration of many
analytes. Immediate analysis of AWD samples is best and chemical preservation should be used only when the preservation is
shown not to interfere with the analysis being performed. Samples collected for total and methyl mercury determinations are to
be collected directly into specially cleaned, pretested, fluoropolymer bottle(s) (19 and 20).
Annual Book of ASTM Standards, Vol 11.01.Reagent Chemicals, American Chemical Society Specifications , American Chemical Society, Washington, DC. For
suggestions on the testing of reagents not listed by the American Chemical Society, see Analar Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset, U.K., and
the United States Pharmacopeia and National Formulary, U.S. Pharmaceutical Convention, Inc. (USPC), Rockville, MD.
Annual Book of ASTM Standards, Vol 11.03.
The boldface numbers in parentheses refer to the list of references at the end of this standard.
D5012–01 (2008)
7.2 Samples Collected for Inorganic Cation and Anion Determinations:
7.2.1 Samples collected for pH, specific conductance, calcium, magnesium, potassium, sodium, chloride, fluoride, and sulfate
analysis are often only placed in pre-cleaned plastic containers (see Section 8) before analysis. If there is a delay between time
of collection and time of analysis, a preservation technique may eliminate or moderate chemical and biological changes in the
AWD samples. Table 1 summarizes the recommended sample preservation techniques for AWD samples.
7.3 Samples Collected for Organic Acids:
7.3.1 Samplescollectedfortheanalysisofacetate,citrate,formateandotherlowmolecularweightorganicacidanions(C -C )
1 12
shouldbepreservedwithinminutesaftercollection.OrganicacidshavebeendeterminedinAWDsamplescollectedfromlocations
around the world (1-7). These compounds (in particular formic and acetic acids) can constitute from a small fraction to mostly all
of the free acidity in AWD samples. Because these acids are unstable in AWD samples, samples must be analyzed within hours
after collection or else a preservation technique is required.Table 2 summarizes the recommended sample preservation techniques
for AWD samples.
7.4 Samples Collected for Trace Dissolved Metals:
7.4.1 Samples collected for trace metals should be filtered to remove insoluble particulate matter often found inAWD samples
unlessanAWDparticulatetraceelementanalysisisdesired.Filterporesizeshouldbe#0.45µm.Filtermaterialsmaycontaintrace
elements, and the filters should be preconditioned before use by filtering 300 mL of water in order to leach soluble impurities on
the filter and from the filtration apparatus itself (8). Any filters used for AWD samples should be tested to determine if the filter
causes losses or gains of trace elements to the AWD sample. Test the preconditioned filters by filtering 50 mL of water and
determine the analyte concentrations of interest in the filtrate.
7.4.2 Acidify theAWD sample with nitric acid to pH#2 to minimize container adsorption of trace metals. The highest purity
acid available should be used. Most AWD samples are poorly buffered and only small quantities of acid (about 1 mL/L) are
required to reduce theAWD sample to a pH#2. Samples acidified with an acid may not be used for the determination of pH and
certain other analytes.
7.4.3 Acidify the AWD sample with 5 mL/L of pretested HCl for dissolved mercury and total mercury.
8. Sample Containers
8.1 ManyAWD sampling networks use samplers that utilize either a bucket or bottle that is an integral component of theAWD
samplers. These collection techniques allow “wet-only” samples to be obtained, meaning the bucket or bottle is only exposed to
the atmosphere during the precipitation event. The preparation or cleaning procedures described in Section 8 apply to the
automated AWD samplers that use buckets, and the sample storage bottles to which the AWD sample is transferred from the
collection bucket. The procedure described in 8.3 could also be used as a cleaning procedure forAWD sampling that uses a bottle
as the principal collection container.
NOTE 1—Any materials used for the collection and preservation of AWD should be dedicated to the use intended.
8.2 Inorganic Ions—Buckets and Lids:
8.2.1 Sample containers shall be made of materials that will not contaminate the sample and shall be cleaned thoroughly before
use. Plastic containers of polyethylene and polypropylene are recommended forAWD samples collected for inorganic ions. HDPE
is most commonly used.
TABLE 2 Preservation of AWD Samples Collected for Organic Acid Determinations
Preservation Technique Species Determined Remarks Reference
HgCl or tetrachloromercu- Low molecular weight acids AWD samples preserved with Hg (II) can be analyzed by capillary GC-MS or (1,2)
rate (Na HgCl ) +4°C for low molecular weight organic anions by ion-exclusion chromatography.
2 4
A
storage Sample disposal may be a problem because mercury and its compounds are a
toxic waste. The preservative is usually coupled with sample storage at 4°C.
See Table 1 for dissolved mercury (II) concentration in AWD samples.
Chloroform Acetate, citrate formate, Analysis is usually by ion-exclusion chromatography because chloroform may (3,4)
C –C interfere with capillary GC-MS analysis. This preservative is often coupled with
1 5
sample storage at 4°C. When chloroform treatment is combined with storage in
the dark at 4°C, samples are reportedly stable for 60 days. Final chloroform
concentration in the AWD sample must be 0.2 % by weight.
Chloroform Acetate, citrate, formate, Analysis is usually by ion-exclusion chromatography because chloroform may (3,4)
C –C interfere with capillary GC-MS analysis. This preservative is often coupled with
1 5
sample storage at 4°C. When chloroform treatment is combined with storage in
the dark at 4°C, samples are reportedly stable for 60 days. Final chloroform
concentration in the AWD sample must be 0.2 % by weight.
Freeze at − 20°C Short-chain dicarboxylic acids Analysis is by capillary gas chromatography or GC-MS. Sample must be (6)
C –C completely in the liquid state before sample is prepared for analysis. Maximum
2 12
storage time has not been reported.
Chill at 4°C Low m
...
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